Agriculture

Dwarf plants

With growing global water shortages and decreasing availability of cultivable land caused by the huge increase in the world population (that has now crossed seven billion), scientists are constantly striving to come up with new more efficient ways of growing food plants. These plants should have higher productivity but need lower amounts of water, fertiliser, nutrients and pesticides to grow.

An interesting solution to the problem has been found by  the Purdue University researcher Burkhard Schulz. He has discovered that a certain chemical can be used to reduce the size of the plant without reducing the yield. Schulz  found that propiconazole, a common fungicide, can be  used to create smaller and sturdier corn plants that produce more kernels but consume less water, fertiliser and nutrients to grow. The fungicide is claimed to be harmless to humans as it is commonly sprayed on golf courses to treat fungal dollar spot disease. The chemical works by disrupting steroid production in the plants, responsible for their growth.

Planet Earth drying up!

Scientists working on global weather patterns predict that the glaciers in the Himalayas as well as in Europe and other parts of the world will melt causing major portions of Asia, Africa, USA and South American to turn into uninhabitable deserts. Extreme flooding will occur in some areas and severe droughts in others resulting in millions of deaths. Most animals and plants will vanish and the population on the planet will rise to 9 billion by the year 2050, but it may diminish rapidly thereafter due to mass famines and wars. This is a terrifying scenario if the average temperature on the planet increases by only 4 degrees centigrade. The last time that global temperature increases of this magnitude occurred was 55 million years ago when large amounts of frozen methane were released from deep oceans and caused temperature increases of 5-6 degrees centigrade. This resulted in tropical forests springing up in polar regions, vast areas from southern Africa to Europe turned into desert, and the dissolved carbon dioxide made the oceans so acidic that most sea life was wiped out.

Growing food crops — with sea water

About 98% of water on our planet is sea water, another 1% is brackish water (having more salt than fresh water but less than sea water) and only about 1% is fresh water. As the world population grows from the present 6 billion to 9 billion over the next 50 years, and as global warming results in increased water shortages, man must look for alternative ways to grow food crops. The depletion of fossil fuels will simultaneously result in acute shortages of oil. Both problems can be solved by growing salt tolerant crops.

Although the water near the sea shore is saline, you may have noticed that some plants can grow under those conditions.  Nature has evolved certain genetic mechanisms that make them salt tolerant. Certain plants, known as “halophytes”, can grow in coastal regions, deserts, marshes, brackish aquifers and even in seas and oceans, and can serve as sources of food and oil. Growing them in such areas will not compete with land used for food crops. The identification of salt tolerant genes and their incorporation into wheat, maize or rice can also impart the salt tolerance into food crops, thereby allowing them to be grown in sea water or brackish water. Some halophytes can also help remove salt from soils affected by salinity.

Certain halophytic algae can be sources of biofuels. An Israeli company Seambiotic has succeeded in producing oil from algae which has a yield equivalent to over 5,600 gallons/year from each hectare of land. This compares favourably with palm oil yield of 1,187 gallons/hectare/year, Brazil ethanol yield of 1,604 gallons/hectare/year, and soy oil yield of 150 gallons/ hectare/year).

In the future man will probably rely on the oceans for growing food crops and meeting energy needs.

Is the food bubble about to burst?

The unsustainable use of water and land has led to increased volumes of food crops over the last several decades. This is a bubble, stretched to a point of bursting, and it could send the world spinning into a crisis of unprecedented magnitudes. The World Bank has estimated that about 175 million people in India are able to eat from grain crops only due to overpumping — water being pumped from underground aquifers faster than it is replenished. The water table is therefore receding at an alarming rate. Saudi Arabia had become self-sufficient in wheat by using water from an aquifer.  The source is however running dry, so that the wheat production could stop within 2-3 years.

There are about 1.5 million new mouths to feed every week as the global population grows, aggravating the situation. The unpredictability of weather patterns is adding another serious factor which can send us over the precipice. The heat wave in Moscow of 2010 caused a loss of 40% of their hundred million ton grain crop. Had this happened in India, China or USA, it could have had a devastating impact on world grain production. Food prices have been rising at an alarming rate in most countries, making life miserable for the poor billions. The highly controversial building of dams in India, which would divert water from Pakistan, could eventually lead to a nuclear conflagration between these two nuclear states.

There is urgency to act before it is too late. Answers lie in education, curbing population growth, adoption of modern and sustainable farming techniques, restoration of nature’s balances by cutting carbon emissions, increasing forest, restoring soils, and adopting water conservation methods at all levels.

Sea water for farming in coastal deserts!

Sea water cannot be used directly for irrigation of food crops because of its salt content — but the humid air from it can, even in adjoining deserts! Three large greenhouses have been established in Tenerife, Abu Dhabi and Oman in which the sea water is pumped to evaporators installed in the green houses to create a humid environment for growing a variety of different plants. The humid air is condensed to afford pure water which is stored and then used for watering the plants. A British company, Seawater Greenhouse, is building these greenhouses for a low cost of US$ 5 per square foot and has now added a concentrating solar power plant to run the generator, pumps and provide additional fresh water.

The Ministries of Science & Technology and Agriculture should start similar projects on our coast line.

Sea water for agriculture: advances in reverse osmosis membranes

The world population is expected to reach 9 billion by 2050, creating enormous pressures for crops for food. As sources of fresh water shrink with rivers drying up due to global warming, a catastrophe lies ahead. There is urgent need for science to find viable solutions to this enormous challenge.

One way to convert saline water (sea water or brackish underground water) into salt- free fresh water, useful for drinking or farming, is by a process known as “reverse osmosis”. This involves pumping the saline water through a special polymeric membrane that allows only water molecules to pass through the pores of the membrane, but prevents salt, bacteria and dirt from doing so. However a drawback of this process is that over a period of time, these particles clog up the expensive membrane and damage it. This results in the need of regular costly membrane replacements, increasing costs. Scientists working at the University of California, Los Angeles have now used nanotechnology to develop a new type of reverse osmosis membrane that is covered with small polymeric hairs. These surface hairs move around rapidly in the water pumping process, thereby acting as an in-built brush which prevents the deposition of impurities on the membrane surface. Once commercialised, it may reduce the cost of production of fresh water from sea water, opening up possibilities of its large scale use for agriculture.

Forward osmosis — exciting developments in water purification

As the population of our planet increases, and as the glaciers melt due to global warming threatening our future water supplies, there is growing interest in finding new ways to obtain pure water from sea water. According to 2006 UN report, 2 out of every 3 persons on our planet will be living under water stress conditions by 2025. The oceans cover about 70% of our planet and contain about 97% of the total water resources. Clearly science has an important role to play in developing processes that will allow sea water to be converted to pure water at affordable cost with minimum use of energy.

Osmosis is a process that allows water to flow through a membrane from the side that has low solute (e.g. salt) concentration to the side that has high solute concentration. This natural tendency to equalize the concentrations of solutions on the two sides of the membrane results in a pressure on the membrane known as “osmotic pressure”. The reversal of this process by application of pressure by a pump so that water starts flowing in the opposite direction is known as “reverse osmosis”. It traps salt molecules on one side of the membrane, allowing pure water molecules to pass through. This leads to high concentrations of salt on one side of the membrane and pure water on the other side. The process of reverse osmosis has been widely employed for production of drinking water from sea water. However there is a problem. The process is costly since it consumes a considerable amount of energy, and the membrane used is costly and has to be regularly replaced as it has a limited life.

An exciting breakthrough has occurred in this field, involving a “going with the flow” (“forward osmosis”) approach instead of trying to oppose it! This involves placing a high concentration of another solute (such as sugar) on one side of the membrane with salt water on the other side. This results in the natural forward flow of water from the side containing salt water to the side containing the solute, such as sugar, resulting in a process for the preparation of soft drinks from sea water through forward osmosis. This process which harnesses the energy gradient, instead of opposing it, consumes up to 80% less energy because the pump pushes the water through the membrane in the same direction as its natural flow tendency.

Hydration Technology Innovations in Albany, Oregon, USA was one of the first companies to use this technology. US soldiers started using “X-packs” that contain sugar and flavours on one side of the forward membrane. When such packs are dipped in sea water, or even in a dirty puddle of ordinary water, they suck pure water molecules into the pack leaving salt and dirt particles behind, thereby creating a pure sweet flavoured drink.

Another important development has been to use removable chemicals such as ammonium bicarbonate in larger plants which draw pure water across the membrane from the salt containing side to the side containing ammonium bicarbonate. This chemical can later be removed and recycled by simple heating, leaving pure water behind. Oasys, a company based in Cambridge, Massachusetts, is building the first demonstration plant based on this process which will start functioning in 2011. 

Water desalination — employing carbon nanotubes!

The two commonly used processes for removing salt from saline water (desalination) are thermal distillation and reverse osmosis. In the first process, the salt water is heated to boiling point and the steam generated is collected by condensation leaving the salt behind. In the second reverse osmosis process, the salt water is pumped through a special “semipermeable” membrane that allows only pure water to pass through while the salt is left behind. Both processes use a considerable amount of energy and are therefore not considered environmentally friendly.

Now scientists working in the New Jersey Institute of Technology in USA have developed a process which can be considered to be intermediate between the two processes mentioned above. Hot saline water is passed through a special semipermeable membrane that has built-in carbon nanotubes to allow greater permeability. The result is a process that allows flow rates that are six times higher than those achieved in conventional membranes.

A self-watering desert plant!

The desert rhubarb (Rheum palaestinum) found in the Negev desert in Israel has leaves which can reach one metre in diameter, whereas other desert plants have small and spiky leaves. Israeli scientists have discovered that it has a unique self-watering mechanism that allows this to happen. They claim that this is the first example of self-irrigation in a plant ever found. The waxy leaves of the plant have deep and wide channels resembling a mountainous range that allow the droplets of water to be captured and then guided so that they fall on the soil near the roots of the plant. Even in light rain, the water that fell near the roots was ten times more than that fell in other areas near the plant, due to this built-in water harvesting mechanism.

Our wheat crop — at risk!

Our wheat crop may be threatened by a new virulent fungal attack from Iran. The Ug99  wheat rust was first discovered in Uganda in 1999, and has spread with the wind to Iran, where it was discovered two years ago. It is now poised to spread across the borders to Pakistan and Afghanistan. This new disease could spread across Asia, threatening famine for millions. In Pakistan, we need to develop and grow wheat varieties resistant to this fungus. 

Cloning plants by tissue culture

It is now possible to produce thousand of plants commercially without using seeds. A leaf is divided into small pieces, placed in a test tube in a chemical medium containing nutrients and growth hormones. After about 6-8 weeks shoots start to develop which are cut off and placed in another medium. Once the roots have been formed, the plant is transferred to soil in an environment with high humidity, usually a green house. When the leaves have been formed, the plants can usually survive in less humid environment. Plants with certain desirable properties, e.g. colour of flowers, size or taste of fruits etc. can be thus multiplied, since the cloned products produced, being genetically identical, will have the same characteristics as the parent. The procedure works well in the manufacture of orchids, bananas and many other plants and is cost effective because of mass production of plants with desirable traits.

Biotechnology — can it tackle food crisis?

Food crises could start toppling individual governments as well as affect global civilisation. Increasing populations, lower crop yield due to global warming and shrinking arable land areas are combining to create a potentially huge problem that can affect us in profound ways. The world carry-over of stocks in 2008 were only 62 days of consumption. The demand of food is rising much faster than the production of food, with the result that food prices are being pushed up. This is creating severe stresses in countries such as Pakistan with a low per capita income. The ‘green revolution’ of the 1960s and 1970s became possible because of scientific agriculture, and the grain yield per acre grew at an average of 2% per year between 1950 and 1990.However this increase has slowed to a little over 1 % per year after 1990. While genetically modified (GM) crops may result in increased yields in certain crops. it seems unlikely that we will witness the 2-3 fold increase in yields that we saw during the green revolution. The long term solutions may lie in controlling world populations, farmer education, better storage and distribution methods, and control of wastages caused by pest and fungus attack.